[armhf] mvebu: do not register custom DMA operations when coherency is disabled

(Closes: #780858)

svn path=/dists/sid/linux/; revision=22457

debian/changelog

@@ -3,6 +3,8 @@ linux (3.16.7-ckt7-2) UNRELEASED; urgency=medium
   [ Ian Campbell ]
   * Initialise framebuffer console earlier. (Closes: #779935)
   * [xen] Enable Xen MCE log support. (Closes: #779698)
+  * [armhf] mvebu: do not register custom DMA operations when coherency is
+    disabled (Closes: #780858)
 
  -- Ian Campbell <ijc@debian.org>  Wed, 18 Mar 2015 21:07:15 +0000
 

debian/patches/bugfix/arm/mvebu-do-not-register-custom-DMA-operations-when-coherency-is-disabled.patch

@@ -0,0 +1,57 @@
+From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+Date: Thu Mar 12 03:58:12 PDT 2015
+Subject: [PATCH 3.18-stable v2] ARM: mvebu: do not register custom DMA operations when coherency is disabled
+Origin: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/330108.html
+
+This patch is a partial backport of commit ef01c6c36bb8 ("ARM: mvebu:
+remove Armada 375 Z1 workaround for I/O coherency"). This commit was
+merged in v3.19, so kernel versions later than v3.19 are not affected
+by the problem that this commit fixes.
+
+It does not make a lot of sense to backport this commit entirely,
+since it is mainly removing some no longer useful code. However, this
+commit is also making sure that the bus_register_notifier that
+register the custom DMA operations that should be used for HW I/O
+coherency does not get registered when said HW I/O coherency is not
+enabled.
+
+This is particularly critical since we have decided to disable HW I/O
+coherency completely in all kernels < 4.0, to be on the safe side,
+while experimenting a new implementation of the HW I/O coherency in >=
+4.0.
+
+Without this commit, kernels earlier than 3.18 have the custom DMA
+operations normally used for HW I/O coherency registered (they don't
+do cache maintenance operations), while HW I/O coherency is
+disabled. It essentially causes every DMA transfer to transfer
+garbage.
+
+The issue fixed by this commit was introduced by 5ab5afd8ba83 ("ARM:
+mvebu: implement Armada 375 coherency workaround"), but it was not
+visible until now since it didn't cause any problem when HW I/O
+coherency is enabled.
+
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
+Cc: <stable at vger.kernel.org> v3.16..v3.18
+---
+ arch/arm/mach-mvebu/coherency.c | 5 +++--
+ 1 file changed, 3 insertions(+), 2 deletions(-)
+
+diff --git a/arch/arm/mach-mvebu/coherency.c b/arch/arm/mach-mvebu/coherency.c
+index 2ffccd4..01efe13 100644
+--- a/arch/arm/mach-mvebu/coherency.c
++++ b/arch/arm/mach-mvebu/coherency.c
+@@ -448,8 +448,9 @@ static int __init coherency_late_init(void)
+ 			armada_375_coherency_init_wa();
+ 	}
+ 
+-	bus_register_notifier(&platform_bus_type,
+-			      &mvebu_hwcc_nb);
++	if (coherency_available())
++		bus_register_notifier(&platform_bus_type,
++				      &mvebu_hwcc_nb);
+ 
+ 	return 0;
+ }
+-- 
+2.1.0

debian/patches/series

@@ -65,6 +65,7 @@ bugfix/x86/acpi-video-add-disable_native_backlight-quirk-for-samsung-730u3e-740u
 bugfix/x86/acpi-video-add-disable_native_backlight-quirk-for-samsung-510r.patch
 bugfix/x86/acpi-video-disable-native-backlight-on-samsung-series-9.patch
 bugfix/x86/drm-i915-quietly-reject-attempts-to-create-non-pagealigned-stolen-objects.patch
+bugfix/arm/mvebu-do-not-register-custom-DMA-operations-when-coherency-is-disabled.patch
 
 # Arch features
 features/mips/MIPS-Support-hard-limit-of-cpu-count-nr_cpu_ids.patch